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Viscoelasticity of Polymers
Published in Z. Yang, Material Modeling in Finite Element Analysis, 2019
Viscoplasticity models can predict the response of nonlinear, time-dependent polymers, but they require more experimental data to define material parameters. The Bergstrom–Boyce model is one typical viscoplasticity model, which is introduced in this section.
Viscoelasticity and Viscoplasticity
Published in M.S. Rahman, M.B. Can Ülker, Modeling and Computing for Geotechnical Engineering, 2018
Viscoplasticity based models can incorporate the inelastic strains. In a sense, viscoplasticity is the rate-dependent version of plasticity where material exhibits permanent deformations but over time. Viscoplastic constitutive equations are used to model the behavior of materials that are subjected to stresses at high temperatures and to model the behavior of materials that are deformed at high strain rates.
Rock creep mechanics
Published in Xia-Ting Feng, Rock Mechanics and Engineering, 2017
Creep is one of the manifestations of viscoplasticity. In practice, it is inextricably linked to stress relaxation. Therefore, to characterize viscoplastic behavior, it is necessary to perform creep test, relaxation test or monotonic compression tests with different rates of loading in appropriate ambient conditions of temperature and humidity. It must be pointed out that conventional tests are mostly performed in compression. Under unloading conditions, reverse creep tests (extension) would be more representative of the actual stress path.
A historical review of the traditional methods and the internal state variable theory for modeling composite materials
Published in Mechanics of Advanced Materials and Structures, 2022
Ge He, Yucheng Liu, T. E. Lacy, M. F. Horstemeyer
In contrast to classical plasticity theory, the theory of viscoplasticity describes the creep flow of continua that is time dependent. The mathematical description of the composites viscoplasticity probably first appeared in the works of Aboudi [86, 87]. In particular, he employed the micromechanics method (fibers were assumed to have rectangular cross sections and were distributed periodically in the matrix) to give the stress-strain relations of the bulk composites in terms of the inelastic behaviors of each constituent. Essentially, the inelastic constitutive equations for each phase were following the unified viscoplasticity theory proposed by Bodner and Partom [88] for single phase materials. Because for viscoplastic materials, the concept of an elastic limit or the initial yield stress is no longer strictly applicable [89]. Bodner and Partom [88] described the viscoplasticity by directly giving a relation between effective inelastic deformation rate and the effective stress, instead of defining the yield function which is commonly used in classical plasticity.
On capturing rate-dependent anisotropic behavior of sheet metal forming using a viscoplastic computational framework
Published in Mechanics of Advanced Materials and Structures, 2022
Leonardo Gunawan, Tatacipta Dirgantara, Sigit P. Santosa, Fauzan Adziman, Ditho A. Pulungan
Viscoplasticity is classified as a time-dependent plasticity model, in which plastic yield strength of the material depends on the loading rate [30]. In this work, the Cowper-Symonds viscoplastic model is adopted since it can accurately describe the material behavior at various strain rates with only few numbers of parameters required [31–36], as shown below.